Before I go any further, I need to make it apparent that A: This is not entirely intended to be taken seriously, rather it's intended to satirize the crappy game mechanics of halo: combat evolved. So on that note, there's no garantee of balance.
Rule 1: From A Distance:
Damage on ranged attacks decreases by -2 for every 5 feet away from the target. Yep, you gotta' be close enough to makeout with your foe if you want to shoot them apparently.
Rule 2: Grenandes Are The Flamming Balls Of God:
Anything that does splash damage requires those caught in the splash damage to make a fortitude saving throw or die.
Rule 3: Only Melee If You Know How:
Melee attacks take a -4 attack penalty. -6 if it's a reach melee weapon. But requires the foe make fortitude save or die. Even if they succeed, they take an additional +8 damage.
Rule 4: No Shields Must Be Tons Of Fun:
If you choose to use this varaint, reduce the total HP you'd have otherwise by -5, and all attacks deal an additional +5 damage. Ranged attacks deal +10 damage instead.
Rule 5: Shields On Means I'll Be Ok:
Like 4th edition. Third edition characters gain healing surges. They gain a number of healing surges equal to their constitution modifier. And heal a number of HP when they activate it equal to their con+str mod combined. (The total healing surge can be no lower then 1hp) Either way, regardless of how much HP you can recover. You only recover 1hp per round.
Rule 6: Rockets Make Everything Better:
The Rocket Launcher is a common weapon. So common that it doesn't cost anything like the club. Here are it's stats.
Damage: 2d12. Critical: -- Multiplyer: -- Ammunition Capacity: 2. Range: 200ft.
Special 1: If the foe makes contact with the rocket launcher. Even just synged by the edge or something, make a fortitude saving throw equal to damage dealt or die. Even if they succeed on the saving throw. The damage dealt is doubled.
Special 2: Rocket Launchers are friggin big. So big that they grant your foes concealment. (20% miss chance)
Special 3: There is a 25% chance you will hit yourself with the rocket launcher regardless of whether or not you hit your opponent. As special 1, you'll need to make a fortitude save, and either way, take double damage.
Reload Time: It takes you four rounds to reload a rocket launcher. Make your time.
Rule 7: Is He Having A Stroke?
Whenever you take damage, make a reflex save. If you fail, you shift 1d4 squares in a random direction (sqaure=10 feet). If you die when you're hit, you shift 1d8 squares instead, and fall prone.
Rule 8: Heroes Are Fat:
You take a -4 penalty to strength and dexterity based skillchecks.
Rule 9: I Can Take a Bullet, But That Five Foot Drop Looks Scary!
For every five feet you would drop, you take 1d10 falling damage. If you drop more then twenty feet, making a reflex saving throw or die.
Rule 10: Invisibility=The hack0rz:
Invisibility spell and greater invisibility "cloak" people, but can the outline of them can be seen with a spot check DC 10.
I'll make more when i'm inspired.